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Fast magnetic skyrmions in synthetic antiferromagnets

    Skyrmions have been the focus of a lot of research works in spintronics in the past few years. Their potential in magnetic information processing makes them an ideal candidate for computing and storing information in nanoscale devices. Skyrmions are defined as topologically non-trivial spin textures, which size allow them to demonstrate particle-like properties.

    However, ferromagnetic (FM) skyrmions are subject to several limitations; the skyrmion Hall effect for example is a source of perturbation regarding their dynamics and skyrmion diffusion displays low speed, not exceeding 100 m/s. However, a group of researchers from Université Grenoble Alpes, CNRS, CEA, SPINTEC, led by Olivier Boulle, managed to reach velocities up to 900 m/s, paving the way for fast manipulation of skyrmions in tracks. They were able to achieve these speeds by using synthetic antiferromagnets (SAF).

    Pairs of antiferromagnetic skyrmions sent on a magnetic track by an electric current. Credits : Bruno Bourgeois and Olivier Boulle – CNRS.

    SAF consists in several FM nanometric layers separated by a nonmagnetic spacer, the layers are coupled to each other through a Ruderman-Kittel-Kasuya-Yosida (RKKY)–type interlayer interaction. In optimized SAF, the skyrmions do not suffer from the skyrmion Hall effect and can be driven by spin-orbit torque thus allowing them to almost tenfold their velocity in classical FM materials.

    “Now we want to demonstrate that we can build a skyrmion-based memory and computing device” research scientist Olivier Boulle said in his interview given for Le Monde. “We are currently working on speech recognition or picture recognition using multiple skyrmions, by exploiting their responses to external stimuli like a voltage”.

    Original article: Fast current-induced skyrmion motion in synthetic antiferromagnets | Science